Yes, there will be no issues with the durability of this product. Streamlight is one of the most reliable light manufacturers in the world.
Yes, any Arisaka mounts designed for the Surefire scout will work for this light. I prefer the in-line or picatinny offset.
No, this flashlight is not waterproof.
The Streamlight ProTac Rail Mount 2 Long Gun Light comes with 2 CR123A batteries.
The Streamlight ProTac Rail Mount 2 Long Gun Light mounts to picatinny rail. If you have a MLOK handguard the MLOK to picatinny section at the link below will allow the Streamlight ProTac Rail Mount 2 Long Gun Light to mount.
https://www.opticsplanet.com/magpul-mlok-hand-guard-rail-section.html
The Streamlight ProTac Rail Mount 2 Long Gun Light does have the TEN TAP programming system.
The Streamlight ProTac Rail Mount 2 Long Gun Light will mount to picatinny rail. So for it to mount to an MLOK rail you will need a MLOK to picatinny rail adapter. The one at the link below will work.
https://www.opticsplanet.com/mdt-aluminum-picatinny-m-lok-rail.html
A 3-Slot M-LOK rail would be able to fit this Streamlight ProTac Rail Mount 2 Long Gun Light. A 5-slot would allow for a little more adjustability but is not required to fit this light to an M-LOK rail. The pressure switch can be fitted without the use of a picatinny rail adapter. The kit includes double sided tape and zip ties to allow you to secure the switch to any part of your rail system.
No, the Streamlight ProTac Rail Mount 2 Long Gun Light only runs on two CR123A batteries.
The Streamlight ProTac Rail Mount 2 Long Gun Light mounts to picatinny rail and not M-LOK. You could use and M-LOK to picatinny rail adapter like the one listed below.
https://www.opticsplanet.com/seekins-precision-aluminum-m-lok-5-slot-rail-section.html